Photoconductive elements containing polymeric binders

ABSTRACT

PHOTOCONDUCTIVE ELEMENTS CONTAINING A PHOTOCONDUCTOR AND A BINDER FOR THE PHOTOCONDUCTOR COMPRISING A POLY(ALKYLIDENEBISARYLOXYALKYL-CO-ALKYLENE ISOPHTHALATE) ARE DESCRIBED. THE DESCRIBED ELEMENTS CAN BE SENSITIZED AND CHARGED EITHER NEGATIVELY OR POSITIVELY AND USED TO PREPARE IMAGES ELECTROPHOTOGRAPHICALLY.

U d St Paten .Qfi

US; crab-1.6 16 can,

ABSTRACT OF THE DISCLOSURE Photoconductive elements containing aphotoconductor and a binder for the photoconductor comprising a poly-(alkylidenebisaryloxyalkyl-co-alkylene isophthalate) are described. Thedescribed elements can besensitized and charged either negatively orpositively and usedto prepare images electrophotographically.

Patented Nov. 21 1972 speeds. In particular, substantial increases inspeeds are obtained as compared to Ispeeds attainable with many otherpolymeric binder compositions. Thesejncreases in speed are observed whenthe coating accepts a suitable potential (e.g., 500-600 volts) and therelative speed o the coating is determined on the basis of thereciprocal of. the exposure required to reduce the potential ofv thesurface charge by 100 volts (shoulder speed) or to 100 volts (toespeed). The reduction of the surface potential to 100 volts or below issignificant in that it represents a requirement for suitable broad areadevelopment of a latent image. The relative speed at 100 volts is ameasure of the ability to produce and henceforth to develop or otherwiseutilize the latent image. When the photoconductor is absent from thecoating and only a coi'lventional binder is used, the surface potentialdoes not'fdroptoor below l00 volt's and therefore no speedjeanibeiassigned This is a continuation of application Ser. No. 772,370,I

filed Oct. 16, 1968, and now abandoned.

.',This inventionirelates to novel electrophotographic ele-' mentshaving coatings of binder-containing photoconduc: tive compositions.

, Binder-containing photoconductive compositions have been widely usedin the preparation of electrophotographic elements. In'electrophotographic reproduction processes, these elements are utilizedin the formation of latent elec-' trostatic images. In some applicationsthe photoconductive compositions contain an organic photoconductor and asensitizer uniformly admixed in an inert resinous binder. (B)

Many binders are currently used in'connection with awide va'rietyyofavailable organic photoconductor compounds and compositions. Typicalbinders are ordinary polymeric materials, e.g., phenolic resins, ketoneresins, acrylic ester resins, polystyrene, etc. However, these bindersusually do I not impartany particular improvement in light sensitivityto'the system. The light sensitivity as indicated by the electricalspeed ofthese particular systems is ordinarily due wholly to the organicphotoconductor and sensitizer. Other binders have been found tocontribute significantly to the light sensitivity of thesystem."However, the selection of these'polymers for incorporation intophotoconductive compositions to form electrophotographic layers hasproceeded on a compound-by-compound basis. Nothing has yet beendiscovered from thenumerous binders tested which permits efiectiveprediction and selection of particular polymers exhibiting the desiredproperties.

It is, therefore, an object of this invention to provide improved novelbinder-containing photoconductive compositions which exhibit high lightsensitivities.

It is another object to provide transparent electrophotographieelementshaving the high speed characteristic of the novel photoconductivecompositions of this invention.

These and other objects of this invention are accomplished by aphotoconductive composition which contains a photoconductor admixedwitha binder therefor which is a poly(alkylidenebisaryloxyalkyl-co-alkyleneisophthalate (wherein the alkylene moiety contains 2 to 10 carbon atoms.It has been discovered that such compositions exhibit increased lightsensitivities as evidenced by greater to such a composition. When aphoto'c'ondu'c'tor is par't'of the coating in many conventionalpolymeric hinders, the surface potentials of such resultant compositionsusually drop below 100 volts, and thus, a definite speed can beascertained. However, these speeds are improved when the binders of thisinvention are employed.

i The poly(alkylidenebisaryloxyalkyl co alkylene isophthalate)copolyes'ters of this invention include those consisting essentially ofthe following repeating units:

and"

wherein Z is an alkylene group having 2 to 10 carbon atoms includingsubstituted as well as unsubstituted alkylene radicals such as g (a)- Astraight chain or branched chain alkylene hydrocarbon radical, e.g.,those represented by the formula:

I TZ T where R, and R are either hydrogen'or an alkyl radical having 1to 5 carbon atoms, 1 is an integer from 1 to 7 and s is an integer fromzero to 7, including a trimethylene radical, a tetramethylene radical, apentamethylene radical, a neopentylene radical, an ethylene radical, a

, hexamethylene radical, a propylene radical, etc.;

('b)- An ox'y'dialkyleneradical or a thiadialkylene radical, e.g.,thoserepresented by the formula where each of and R is an alkylene radicalincluding a branched 'chain alkylene CHCH2" etc. where- D is an oxygenor sulfur atom and n and o are integers from 2 to 7 including anoxydiethylene radical, a thiadiethylene radical, etc.;

(c) An alkylene bis(o xyalkylene) radical or an alkyleriebisfihiaalkylenradical, e.g.,those"represented by the formula where Q isthe atoms necessary to complete a 3 to 6 carbon cycloalkylene radicaland u and v are integers from to 5, including a cyclohexylenedimethyleneradical, a cyclopentylenedimethylene radical, acyclobutylene-dini'ethyleneradical, a' cyclobutylenediethylene radical,a

is coated on an electrically conducting support in a wellknown manner,such as swirling, spraying, doctor blade coating, and the like.

The novel binders of this invention improve the electrical speeds ofcompositions containing a wide variety of photoconductors.includinginorganic photoconductors such as zinc oxide, titanium dioxide, cadmiumsulfide and the like and organic photoconductors includingorganometallic photoconductors.

Typical photoconductors useful with the binders of this invention aredescribed below.-

(A) Arylamine photoconductors including substituted and unsubstitutedarylamines, diarylamines, nonpolymeric triarylamines and polymerictriarylamines such as those cyclobutylene radical, 2,2,4,4-te.tramethyl1,3-cyclobutylene radical, etc.;

' (e) *D and E each can be ahydrogen atom, a halogen atom, an alkylgroup, an aryl group, an alkoxy group or an .aryloxy group. I Thecopolyester binders of this invention suitably contain'2"to 80% andpreferably 30 to 60% of repeating unit A. The binder also suitablycontains from about 20 to 98% and preferably 40 to 70% of repeating unitB. The polymer contains these units arranged in a random, linearfashion. Binders comprising such polymers improve the electrical speedof the photoconductive composition.

Exemplary of a few of the many polymers useful as binders in thisinvention are: I

( 1 Poly(4,4-isopropylidenebisphenoxyethyl-co-tri- .methyleneisophthalate) (2)Poly(4,4-isopropylidenebisphenoxyethyl-co-tetramethylene isophthalate)(3) Poly(4,4'-isopropylidenebisphenoxyethyl-co-ethylene isophthalate)(4) Poly(4,4'-isopropylidcnebisphenoxyethyl-co-oxy- --diethyleneisophthalate) e (5) Poly(4,4'-isopropylidenebisphenoxyethyl-co-neopentylisophthalate) (6)Poly(4,4-isopropylidenebisphenoxyethyl-co-cyclohexylenedimethyleneisophthalate) (7)Poly(4,4-isopropylidenebisphenoxyethyl-co-cyclobutylenedimethyleneisophthalate) (8)Poly(4,4'-isopropylidenebisphenoxyethyl-co-thiadiethylene isophthalate)(9) Poly[4,4'-isopropylidenebisphenoxyethyl-co-ethyl enebis(oxyethylene)isophthalate] 10) Poly[4,4-isopropylidenebisphenoxyethyl-coethylenebis(thiaethylene)isophthalate] (1 1) Poly(4,4'-isopropylidenebisphenoxyethyl-co- 2,2,4,4-tetramethyl-1,3-cyclobutylene isophthalate) (l2)Poly(4,4'-isopropylidenebisphenoxyethyl-co-tetramethylene-4-bromoisophthalate)7 13) Poly(4,4'-isopropylidenebisphenoxyethyl-cdtetramethylene-5-phenoxyisophthalate) (14)Poly(4,4'-isopropylidenebisphenoxyethyl-copropylene isophthalate) 15)Poly(4,4-isopropylidenebisphenoxyethyl-cotetramethylene-Z,S-dichloroisophthalate)l 6)Poly(4,4'-isopropylidenebisphenoxyethyl'cotetramethylene-5-methoxyisophthalate)17) Poly(4,4'-isopropylidenebisphenoxyethyl-cotetramethylene-5-phenylisophthalate)In preparing typical electrophotographic elements utilizing thepolymeric binders of this invention, an organic photoconductor isdissolved in a solution of binder and solvent and then, after thoroughmixing, the composition described in US. Pats. 3,240,597 and 3,180,730.

(B) Photoconductors represented by the formula wherein A represents anononuclear or polynuclear divalent aromatic radical, either fused orlinear (e.g., phenyl, naphthyl, biphenyl, binaphthyl, etc.), or asubstituted divalent aromatic radical of these types wherein saidsubstituent can comprise a member such as an acyl group having from 1 toabout 6 carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkylgroup having from 1 to about 6 carbon atoms (e.g., methyl, ethyl,propyl, butyl, etc.), an alkoxy group having from 1 to about 6 carbonatoms (e.g., methoxy, ethoxy, propoxy, p entoxy, etc.), or a nitrogroup; A represents a mononuclear or polynuclear monovalent orpolynuclear monovalent aromatic radical, either fused or linear (e.g.,phenyl, naphthyl, biphenyl, etc.); or a substituted monovalent aromaticradical wherein said substituent can comprise a member, such as an acylgroup having from 1 to about 6 carbon atoms (e.g., acetyl, propionyl,butyryl, etc.), an alkyl group having from 1 to about 6 carbon atoms(e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from1 to about 6 carbon atoms (e.g., methoxy, propoxy, pentoxy, etc.), or anitro group; Q can represent a hydrogen atom or an aromatic amino group,such as A'NH; b represents an integer from 1 to about 12, and Lrepresents a hydrogen atom, a mononuclear or polynuclear aromaticradical, either fused or linear (e.g., phenyl, naphthyl, biphenyl,etc.), a substituted aromatic radical wherein said substituent comprisesan alkyl group, an alkoxy group, an acyl group, or a nitro group, or apoly(4'-vinylphenyl) group which is bonded to the nitrogen atom by acarbon atom of the phenyl group, these materials being more fullydescribed in US. Pat. 3,265,496.

(C) Polyarylalkane photoconductors including leuco bases of diaryl ortriarylmethane dye salts, 1,1,1-triarylalkanes wherein the alkane moietyhas at least two carbon atoms and tetraarylmethanes having an aminogroup substituted in at least one of the aryl nuclei attached to thealkane and methane moieties of the latter two classes of photoconductorswhich are non-leuco base materials; and also other polyarylalkanesincluded by the formula:

I) J-d-E wherein each of D, E and G is an aryl group and I is a hydrogenatom, and alkyl group, or an aryl group, at least one of D, E and Gcontaining an amino substituent, the aryl groups attached to the centralcarbon atom being preferably phenyl groups, although naphthyl groups canalso be used, including substituted aryl groups containing substituentssuch as alkyl and alkoxy typically having 1 to 8 carbon atoms, hydroxy,halogen, etc. in the ortho, meta or para positions, ortho-substitutedphenyl being preferred; the aryl groups can also be joined together orcyclized to form a fiuorene moiety, for example; the amino substituentcan be represented by the formula wherein each R can be an alkyl grouptypically having 1 toj8 carbon atoms, a hydrogen atom, an aryl group, ortogether the necessary atoms to form a heterocyclic amino group'typically havingi to 6 atoms 'in the ring such as "morpholi'nofpy'ridyl, pyrryl, etc.'; at least one of D, E and G" preferably being ap-dialkylami'nophenyl group," when I is an alkyl group, such an alkylgroup more generally has to" 7 carbon atoms, "these materials being morefully described in U.S. Pat-3,274,000, French 'Pat. 1,383,- 46 1 andiIlZUZS. Ser.1No. 627,857 filed Apr. 3, ,1967 by Seus aiiq Goldman nowUS. 3,542,544. Photoconductors comprising 4-diarylamino sub- 'st'itutedchalcones'havingthe formula: i t

' \Nfli JD wherein R and R are each phenyl, radicals includingubstitutedphenyl radicals" and particularly whenR is a phenyl radicalW.herein R and R areeach aryl radicals, aliphatic resi- .-dues of H012carbon atoms such .as alkyl radicals prefer- :ablyhaving v1 to 4 carbonatoms, or hydrogen; particularly advantageousaresults beingobtained-when R; is a vphenyl radical including-a substituted phenylradical and where ;;R ,is diphenylaminophenyl, dimethylaminophenyl or tyis a conjugated triene with no aromatic structure fused thereto.However, if there isat least one aromatic structure fused tothecycloheptenyl moiety, then the substituents are attached to a saturatedcarbon atom. Additional photoconductors within this class areincluded'in one of the following formulae: Y

6 where E and G can be either:

(a) A phenyl radical,

(b) A naphthyl radical,

(c) A heterocyclic radical having 5 to 6 atoms in the heterocyclicnucleus and at least one hetero nitrogen atom,

(d) A hydroxyl radical, or

(e) An oxygen containing radical having a structure such that theresultant cycloheptenyl compound is a symmetrical ether;

D can be any of the substituents defined for E and G above and isattached to a carbon atom in the cycloheptenyl nucleus having a doublebond; (R and R (R and R (R and Re), and R and R are together thenecessary atoms to complete a benzene ring fused to the cycloheptenylnucleus; these compounds being more fully described in U.S. Ser. No.654,091 filed July 18, 1967 now U.S. 3,533,786.

.' (F) Compounds containing an nucleus including (1) unsubstituted andsubstituted N,N- bicarbazyls containing substituents in either or bothcarbazolyl nuclei such as (a) An alkylradical including a substitutedalkyl radical such as a haloalkyl or an alkoxyalkyl radical,

(b) A phenyl radical including a substituted phenyl radical such as anaphthyl, an aminophenyl or a hydroxyphenyl radical,

(c) A halogen atom,

(d) An amino radical including substituted as well as unsubstitutedamino radicalssuch as an alkylamino or a phenylalkylamino radical,

"'(e) An 'alkoxy radical, (f) A hydroxyl radical,

. (g) A cyano radical,

NN El ill where D E G and" J are each either i (a) A substituted phenylradical such as a naphthy radical, an alkylphenyl radical, a halophenylradical, a hydroxyphenyl radical, a haloalkylphenyl radical or ahydroxyalkylphenyl radical or (b) A heterocyclic radical such as animida zolyl radical, a furyl radical'ora pyrazoline radical. Inaddition, J and E can also be (c) An unsubstituted phenyl radical.Especially preferred are those tetra-substituted hydrazines wherein bothD and G are either substituted phenyl'radicals or heterocyclic radicals.These compounds are more fully described in U.S. Ser. No. 673,962 filedOct. 9, 1967 now U.S. 3,542,546.

(G) Organic compounds having a 3,3'-bis-aryl2F pyrazoline nucleus whichis substituted in either fivemember ring with the same or dilferentsubstituents. The 1 and 5 positions on both pyrazoline rings can besubstituted by an aryl moiety including unsubstituted as well assubstituted aryl substituents such as alkoxyaryl, alkaryl, alkaminoaryl,carboxyaryl, hydroxyaryl and haloaryl. The 4 position can containhydrogen or unsubstituted as well as substituted alkyl and aryl radicalssuch asralkoxyaryl, alkaryl, alkaminoaryl, haloaryl, hydroxyaryl,alkoxyalkyl, aminoalkyl, carboxyaryl, hydroxyalkyl and haloalkyl. Otherphotoconductors in this class are represented by the followingstructure:

wherein D D 1;, and J can be either a phenylradical including asubstituted phenyl radical such as a tolyl radical or a naphthyl radicalincluding a substituted naphthyl radical, I

E E G G L and L can be any of the substituents set forth above and inaddition can beeither a hydrogen atom or an alkyl radical containing 1-8carbon atoms. These organic photoconductors are more fully described inUS. Ser. No. 664,642 filed Aug. 31, 1967 now US. 3,527,602.

(H) Triarylamines in which at least one of the aryl radicals issubstituted by either a vinyl radical or a vinylene radical having atleast one active hydrogencontaining group. The phrase vinylene radicalincludes substituted as well as unsubstituted vinylene radicals and alsoincludes those radicals having at least one and as many as threerepeating units of vinylene groups such as wherein n is an integer offrom one to three. Groups which contain active hydrogen are well knownin the art, the definition of this term being set forth in several textbooks such as Advanced Organic Chemistry, R. C. Fuson, pp. 154-157, JohnWiley & Sons, 1950. The term active hydrogen-containing group as usedherein includes those compounds encompassed by the discussion in thetextbook cited above and in addition includes those compounds whichcontain groups which are hydrolyzable to active hydrogen-containinggroups. Typical active hydrogen-containing groups substituted on thevinylene radical of the triarylamine include:

(a) Carboxy radicals, (b) Hydroxy radicals, (c) Ethynyl radicals, (d)Ester radicals (e.g.,

wherein R is alkyl or aryl) including cyclic ester radicals (e.g.,

l? CCl etc.), and

(i) Amido radicals (e.g.,

ll -CN wherein R is a hydrogen atom, an alkyl group or an aryl group).Other active hydrogen-containing groups include substituted andunsubstituted alkylidyne oximido radicals. Photoconductors included inthis class can be represented by the following structure: I

NAr o=o X Ag ie 17)n wherein: (a) Ar and Ar are each a phenyl radicalincluding a substituted phenyl radical such as a halophenyl radical, analkyl phenyl radical or an aminophenyl radical;

(b) Ar is an arylene radical including a substituted arylene radicalsuch as a phenylene radical or a naphthylene radical,

(c) R and R are each hydrogen, a phenyl radical including a substitutedphenyl radical or a lower alkyl radical preferably having 1-8 carbonatoms;

(d) X is either (I) an active hydrogen-containing group such as acarboxy radical, an acyl halide radical, an amido radical, a carboxylicacid anhydride radical, an ester radical, a cyano radical, a hydroxyradical, a semicarbazono radical, an ethynyl radical, or a methylidyneoximido radical, or (2) hydrogen, provided that when X is hydrogen R andR are also hydrogen; and

(e) n is an integer of one to three.

The arylene nucleus can be substituted in any position by the vinyl orvinylene moiety. However, when Ar is phenylene, particularly goodresults are obtained if the substitution occurs in the para position.These materials are more fully described in US. Ser. No. 706,800 filedFeb. 20, 1968 now US. 3,567,450.

(I) Triarylamines in which at least one of the aryl radicals issubstituted by an active hydrogen-containing group. The term activehydrogen-containing group has the same meaning as set forth above andagain includes those compounds encompassed by the discussion in thetextbook and additionally includes those compounds which contain groupswhich are hydrolyzable to active hydrogen-containing groups. Typicalactive hydrogencontaining groups which are substituted on an arylradical of the triarylamine include:

(a) Carboxy radicals;

(b) Hydroxy radicals;

(c) Ethynyl radicals;

(d) Ester radicals (e.g.,

wherein R is an alkyl or an aryl group);

(e) Lower alkylene hydroxy radicals (e.g., having 1-8 carbon atoms);

(f) Carboxylic acid anhydride radicals;

(g) Lower alkylene carboxy radicals (e.g., having 2-8 carbon atoms);

(h) Cyano radicals;

(i) Acyl halide radicals (e.g.,

etc.);

(j) Amido radicals (e.g.,

0 io t wherein R is a hydrogen atom, an alkyl group or an aryl group);

(k) Lower alkylidyne oximido radicals having 1-8 carbon atoms includingsubstituted alkylidyne oximido radicals (e.g.,

wherein R is hydrogen or a lower alkyl radical);

(l) semicarbazono radicals; and

(m) Arylene carboxy radicals including.- substituted arylene carboxyradicals (e.g.,

wherein R; and B are phenyl or lower alkyl radicals. Photocond'uc'tor'sincluded in this classcan be represented by the following structure: r

- -frxn wherein:

(a) An; and Ar are each a' phenyl radical including a substituted phenylradical such asa halophenyl radical, an alkyl phenyl radical or'an"aminophenyl radical;

(b) Ar is an arylene radical'in'cluding 'a"'substitute'd arylene radicalsuch as a phenyle'ne radical or-va naphthylene radical; and

(c) X is an active hydrogen-containing'groupsuch as a carboX'y radical,an acyl halide-radical, an amido radical, a carboxylicacid'anhydride'radical, an ester radical, a cyano radical, asemicarbazono radical, a hydroxy radical, an ethynyl radical, amethylidyine oximido radical or a phenylene carbox'y radical. Thesematerials are more fully'described in U.S. Ser'.-'No.- 706,780 filedFeb. 20, 1968. r

(J) Organo met'allic compounds having at least one amino-arylsubstituent attached to a: Group IVa or Group Va metal atom; Themetallicsubstituents of this class of organic photoconductbrsare:Gr'oup- IVa orGroup Va metals in accordance'iwithlhe Periodic- Tableof the Elements (Handbook of Chemistry and Physics, 38th edition, pp:394-95) and include silicon, germanium,1tin and lead from Group Na andphosphorus, arsenic,.antimony arid bismuth from Group Va.x ;[hesematerials can be substituted in the metallo nucleus-with a wide varietyof substituents but at leasti'one of thesubstituents must be anamino-aryl radical; The amino radical can bepositioned anywhere on thearomatic 'nucleus,:but best results are obtained if the aryl 'moiety isaphenyl radical ha ving the amino group in the 4 or paraposition:'Iypicalsubstituents, attached to the' -metal---nucleus include ;.thefollowing: :1 s,

(a) A hydrogen, sulfurlor oxygenatom,"-

(c) An aryl radical-includingunsubstituted aswwell as substituted arylradicals such as aminoaryl, alkylar'yland haloaryl, I 1

, (d) An.oxygen-containing.radicalisuch as-an-alkoxy or aryloxy radical,r

(e) An amino radical includingiunsubstituted.and substituted aminoradicals such ast-monoand-diarylamino and monoand dialkylaminoradicals,- r g (f) Aheterocyclic radicaland r 1 (g) A GroupdVaorVaorgano metallicradical; Photoconductors included in? this class can'berepresented by the following structures: r

or I

cti m v fl T-Ar-lYhr G L where E G L and Q can be wherein R and R can behydrogen atomsor alkyl radicals having 1. to 8 carbon at0ms, or

(g) A heterocyclic radical having 5 to 6 atoms in the hetero nucleusincluding at least one nitrogen atom such as a triazolyl, a pyridylradical, etc.;

T is an amino radical such as an alkylamino radical having 1 to 8 carbonatoms or-an arylamino radical such as a phenylamino radical; l

Ar is an aromatic radical such as phenyl or naphthyl;

M and M 2 are the same or ditferentGroup, lVa metals; 3

M is a Group Va metal;

D can be any of the substituents set forth above for E G L and Q and inaddition can be a Group Iva organo-metallic radical or whenytaken atomor a sulfur atom;

J can be any of the substituents p E G L and Q andin addition cambeuwhentaken with B, an oxygen atom or-waisulfur atom-,Theise materials aredescribed in U.S. Ser. No. 650,664fi1ed1uly 13,1967.

(K) Any other organic compound awhich exhibits photoconductiyeproperties such as those-;se't forth in Australian Pat. 248,402.? L v tRepresentative organic photoconductors useful in'this invention includethe compounds listed below: y TABLE I diphenylamine dinaphthylamineN,N'-diphenylbenz idine N-phenyl-l-naphthylamineN-phenyl-2-naphthylamine I N,N'-diphenyl-p-phenylenediamine2-carboxy-S-chloro-4'-methoxydiphenylarnine p-anilin'ophen'ol IN,N-di-2-naphthyl-p-phenylenediamine f r4,4-benzylidene-bis-(N,N-dimethyl m-toluidine) triphenylamineN,N,N,N'-tetraphenyl-m-phenylenediamine 4-acetyltriphenylamine "I4-hexanoyltriphenylamine 3 4-lauroyltriphenylamine 14-hexyltriphenylamine 4-dodecyltriphenylamine4,4'-bis(diphenylarnino)benzil 4,4-bis(diphenylamino)benzophenonevpoly[N,4"-(N,N',N'-triphenylbenzi dine) polyadipyltriphenylaminepolysebacyltriphenylamine anine including. carbocyanine dyes.

, binder and organic photocond s sst hqto raphi e e ,rnix a. suitableamount of ,the coating. composition so 1 31-(p-'dipheiiylaminophe'nyl)ethanol 'dr oxytriph'enylamine Zh'YdTOXytfiphenyIamihe 4-formyltriphenylamine oxime H4-acetyltriphenylamine oximq ,w 5 1-(p-diphenylaminophenyl')hexanol l=(pdiphenylam'inophenyl)dodecanol p-diphenylaminoberizlo ic ac'idanhydride4-cyanotripheriylamine--"' p diphenylaminobenzoic acidN,N-diphenylamide"- p-diphenylaminobenzoic acid-=p-diphenylaminobenzoylchloride 3 p-diphenylaminophenylpropionic acid4-f'ormyltriphenylamine"semicarhazone' triphenyl-'-diethylaminophenylsilane methyl-diphenylp-diethylamino'phenylsilatripheny1+p-diethylaminophenylgermane.tr-iphenyl-p=dimethylaminophenylstanrianetriphenylip-diethylaminophenylstannanediphenyl-di+(p=diethylaminophenybstannaritriphenyl-p-diethylaminophenylplumbanetetra-p-diethylaminophe'nylplumbane1 =1 1? pheny-l-di-(p-diethylaminophenyl) phosphine" .bis(p-diethylaminophenyl)phosphineioxide l tri-pdimethylaminophenylarsinetri=pdiethy1aminophenylarsine ,2yamethyl-4edirnethylaminophenylarsinetrirp-diethylaminophenylbismuthine 1, m lhyl-d-lp-diethylaminophenyl)arsine, methyldi-(paiiethylaminophenyl)phosphinephenyl-triip-diethylaminophenyl.)stannane, methyl-tri(.pdiethylaminophenyl)stannane oXidew e -pe st n op ieny serman diph y-phyl m nqpheny p:di y n pheny ts ne. tetrakis-[diphenyl-.(prdiethylaminophenyl)plumbyl] p methane 1, v r tetrakis-[diphenyl-(pdiethylaminophenyl) stannyll; stannane i 1-1 r bis-[phenyletp-diethylaminophenyl )J dibismuthine' T -(pe ylam no h )posptli sulfide d -(prtl inqphstlyl)t x t n The photoconductive-layers oftheinvention can also 'be sensitized by the addition 'of effectiveamountsof sensitizing compounds to exhibit improved electropho- 4'5tosensitivity. sensitizing compounds useful with the photoconductivecompounds of the present invention can be selected fro'm a" wide varietyof materials,"-including such materials as pyrylium' including'thiapyrylium and "Selena- Pat. 3,250,615; fluorenes," such as"7,12-dioxo-13-dibenzo(a,h)fluorene,5,10-odioxo-4a,1l-diazabenzo(b)fluorene,3,l3-dioxo-fioxadibenzo(b,g)fluorene, ,1 and. the 1 like; aromatic nitrocompounds oft-the kinds :described' inwU.S.Pat. 2,610,120;anthronesylike. those disclosed in! U.'S.Pat-. 112,670,284, :quinones,1U;S., Pat. 2,670,286; benzophenones US. Pat. =-2,67 =,0,28-7j;thiazoles US. Pat. 2,732,301; mineral acids; carboxylic acids, such asmaleic acid dichloroacetie'acid, -andsalicyclicacid;

lsulfonic and phosphoric acids; and various dyes, such as iicvanina (inuding c b syanine2;..19 rqw pigedim -methane, thiazine, azine, oxazine,xanthene phthalein,

acridine, azo, anthraguin one' is and the like and mi tures thereof. Thesensitizers referred for fisewith the compounds of this invention" are'selected'from" pyrylium including selenapyrylium'anduthiapyryliumsalts, and cy- Wh'ere a, sensitizing comp pin the sensitizing "com oim14 coated element; Other methods of incorporating the sensi tizer or theeffect of the sensitizer may, however, be employed con'sistent with thepractice of this invention. In preparing the photoconductive layers, nosensitizing compound is required to give photoconductivity in the layerswhich contain the photoconducting substance therefore, no sensitizer isrequired in a particular photoconductive layer. Howev'en-"sincerelatively minor amounts of sensitizing compound give substantialimprovement in speed in such layers, the sensitizer is preferred. Theamount of sensitizer that canbe added to a photoconductor-incorporatinglayer to give effective increases in speed can vary widely. The optimumconcentration in any given case will vary with .the specificphotoconductor and sensitizing compound used. In general, substantialspeed gains can be obtained where 'an appropriate sensitizer is added ina concentration 'r'ange from about 0.0001 to about 30 percent byweightbased on the weight of the film-forming coating compositionNormally, a sensitizer is added to the coating composition in an amountby weight from about 0.005 to about 5.0 percent by weight of the totalcoating composition.

Solvents usefulfor preparing coating compositions with'the binders ofthe present invention can include a wide variety of organic solvents forthe components of the' -coating' composition. For example, benzene;toluene; acetone; 2-butanone; chlorinated hydrocarbons such as methylenechloride; ethylene chloride; and the like; ethers, such astetrahydrofuran and the like, or mixtures of such solvents canadvantageously be employed in the practice of this invention.

rlnipreparinguthe coating compositions utilizing the binders disclosedherein useful results are obtained Where theiphotoconductive substanceis present in an amount equal toat least about 1 weight percent of thecoating compositiom'l'he upper limit in the amount of photoconductivematerial present can be widely varied in accordance with usual practice..It is normally required that the photoconductive material be present inan amountranging from about 1 weight percent of the coating-compositionto about 99 weight percent of the coating composition. A preferred,.weight range for the conductivelayrs "of the presentinventio'n caninclude any of the electrically "conducting supports," for example,

paper (at a relative humidity above 20 percent); aluminum-paper'lamintes; metal foils, such as aluminum 'foil, zinc' foil,-t-etc-'.;metal plates, such as aluminum, copper, zinc, brass,-'and galvanizedplates; vapor deposited metal layers such as silver, nickel or aluminumon conventional film supports such as cellulose acetate, poly(ethy1eneterephthalate),= polystyrene and the like conducting sup- POrtsr-Y'i Anespecially usefulconducting support can be prepared by coating a filmsupport material such as poly- (ethylene terephthalate)'-with a layercontaining a semiconductor dispersed in a resin. A suitable conductingcoating can be prepared from the sodium saltofa carboxy- .este'r'lactone 'of maleic-anhydride and a vinyl acetate the well knownelectrophotographic processes which require photoconductive layers. Onesuch process is the xerographic process. In a process of this type, anelectrophotographic element held in the dark, is given'a blanketelectrostatic charge by placing it under a corona discharge to give auniform charge to the surface of the photoconductive layer. This chargeis retained byvthe layer owing to the substantial dark insulatingproperty of the layer, i.e., the low conductivity of the layer in thedark. The electrostatic charge formed on the surface of thephotoconductive layer is then selectively'dissipated from the surface ofthe layer by irnagewise exposure to light by means of a conventionalexposure operation such as for example, by a contact-printing technique,or by lens projection of an image, or reflex or bireflex techniques andthe like, to thereby form a latent electrostatic image in thephotoconductvie layer. Exposin-g'the surface in this manner forms apattern of electrostatic charge by virtue of the fact that light energystriking the photoconductor causes the electrostatic charge in the lightstruck areas to be conducted away from the surface in proportion to theintensity of the illumination in a particular area.

The charge pattern produced by exposure is then'developed or transferredto another surface and developed there, i.e., either the charge oruncharged areas rendered visible, by treatment with a medium comprisingelectrostatically responsive particles having optical density.- Thedeveloping electrostatically responsive particles can be in the form ofa dust, or powder and generally comprise a pigment in a resinous carriercalled a toner. A preferred method of applying such a toner to a latentelectrostatic image for solid area development is by theme of a magneticbrush. Methods of forming and using a magnetic brush toner applicatorare described in the following U.S. patents: 2,786,439; 2,786,440;2,786,441; 2,811,465; 2,- 874,063; 2,984,163; 3,040,704; 3,117,884; andreissue Re. 25,779. Liquid development of the latent electrostatic imagemay also be used. In liquid development the developing particles arecarried to the image-bearing surface in an electrically insulatingliquid carrier.'Methods of development of this type are widely known andhave been described in the patent literature, for example, U.S. Pat.2,297,691 and in Australian Pat. 212,315. In dry developing processesthe most widely used method of obtaining a permanent record is achievedby selecting a developing particle which has as one of its components alowmelting resin. Heating the powder image then causes the resin to meltor fuse into or on the element. The powder is, therefore, caused toadhere permanently to the surface of the photoconductive layer. In othercases, a transfer of the charge image or powder image formed on thephotoconductive layer can be made to a second support such as paperwhich would then become the final print after developing and fusing orfusing respectively. Techniques of the type indicated are well known inthe art and have been described in a number of U.S. and foreign patents,such as U.S. Pats. 2,297,691 and 2,551,582, and in RCA Review, vol. 15(1954), pages 469-484.

The compositions of the present invention can be used inelectrophotographic elements having many structural variations. Forexample, the photoconductive composition can be coated in the form ofsingle layers or multiple layers on a suitable opaque or transparentconducting support. Likewise, the layers can be contiguous or spacedhaving layers of insulating material or other photoconductive materialbetween layers or overcoated or interposed between the photoconductivelayer or sensitizing layer and the conducting layer. It is also possibleto adjust the position of the support and the conducting layer placing aphotoconductor layer over a support. and coating the exposed face of thesupport or the exposed or overcoated face of the photoconductor with aconducting layer. Configurations differing from those contained in theexamples can be useful oreven preferred for the same or differentapplication for the electrophotographic element.

The following examples are included for a further understanding of thisinvention. 1

Example' l 1.5 grams ofpoly(4,4-isopropylidenebisphenoxyethylco-tetramethylene isophthalate)binder cointaining 0.5 gram of4,4'-benzylidine-bis(N,N-diethyl-m-toluidine) photoconductor-and .04gram of 2,4 (4-ethoXyphenyl)-6-. (4-n-amlyoxystyryl) pyryliumfluoroborate sensitizer are dissolved in 15.6 grams ofmethylene'chloride by stirring the solids in the solvent'for one hour atroom temperature. The resulting solution is hand coated at a wet coatingthickness of 0.004 inch on a conducting layer'comprising the sodium saltof=a carboxyester lactone, such as described in U.S. 3,120,028, which inturn is coated on' a cellulose acetate film base. The coating blockismaintained at a temperature of F. 'After drying, theelectrophotographic element is charged under positive corona sourceuntil the surface potential, as measured by an electrometer probe,reaches about 600 volts. It is then subjected to exposure from behind astepped density gray scale to a 3000 K. tungsten source. The exposurecauses reduction of the surface potential of the element under each stepof the gray scale from its initial potential, V to some lower potentail,V, whose exact value depends on the actual amount of'exposure inmeter-candle-seconds received by the area.'The results of themeasurements are plotted on a graph of surface potentialV vs. logexposure for each step. The shoulder speed is the numerical expressionof 10 multiplied by the reciprocal of the exposure inmeter-candle-seconds required to reduce the 600 volt charged surfacepotential by volts. The toe speed is the numerical expression of 10multiplied by the'reciproc'al of the exposure in meter-candlesecondsrequired to reduce the 600 volt charged surface potential to 100 volts.This coating is found to" have a positive 100 v. toe speed of 250.Similar results are obtained when 0.5 gram-ofbis(4-diethylamino)-1,1,1-triphenylethaneor 0.5 gram ofbis(4-diethylamino)tetraphenylmethane are used as photoconductors inplace of the 4,4-benzylidine bis(N,N-diethyl-m-toluidine) for bothpositive and negative charging.

I Example 2 Example lis repeated except .that binder employed ispoly(4,4'- isopropylidenebisphenoxyethyl co ethylene terephthalate).This binder does not fall within the scope of the inventionin that theterephthalate is used instead of the isophthalate and is included forcomparison purposes only. The coating has a positive 100 volt toe speedof 128.

The following Examples 3 and 4 are identicalto Example 1 except for thebinder employed. 1.5 grams of various binders are used in each of thefollowing examples. In each case a significant improvement is noted inthe 100 v. toe speeds over binders of the type described in thepreceding example. I

TABLE II V Positive 100 v. toe Example Binder speed 3-Poly'(4-4'-is0propylideneblsphenoxyethyl-co- '20o-'ethYienolsophthalate); 4 Poly(4,4'-lsopropylldenebisphenoxyethyl-co-200 neopentyl isophthalate).

Example 5 The coating compositions of Examples. 1, 3 and 4 are .againcoated iu the manner described inExample 1. In

a darkened room, the surface of each of the photoconducopaque and lighttransmitting areas and exposed to the radiation from an incandescentlamp with an illumination intensity of about 75 meter-candles for 12seconds. The resulting electrostatic latent image is developed in theusual manner by cascading over the surface of the layer a mixture ofnegatively charged black thermoplastic toner particles and glass beads.A good reproduction of the pattern results in each instance.

Example 6 The copolyesters described herein are made by standard meltcondensation techniques. Poly(4,4'-isopropylidenebisphenoxyethyl coethylene isophthalate) is prepared by miXing 0.15 mole of dimethylisophthalate, 0.075 mole of 4,4 isopropylidenebisphenoxyethanol, 0.10mole of ethylene glycol and 0.05 gram of tetrabutyl orthotitanate.Nitrogen is bubbled through the mixture,

and -98% of CHz-OHg-OGigQO-OHpCHg-O-ii- E O and it is heated at 200 C.for 2 hours to distill off methanol. The temperature is raised to 250 C.and vacuum applied until complete polymerization is completed. Theresultant polymer contains 50% of repeating unit A and 50% B. The otherpolymers are prepared by the same method by replacing ethylene glycolwith the appropriate compound. For example, trimethylene glycol would beused to prepare polymer 1, tetramethylene glycol for polymer 2,diethylene glycol for compound 4, etc.

The invention has been described in detail with particular reference topreferred embodiments thereof but it will be understood that variationsand modifications can 'be effected within the spirit and scope of theinvention as described hereina-bove and as defined in the appendedclaims.

I claim:

1. An electrophotographic element capable of reproducing continuoustones comprising a support having coated thereon a photoconductivecomposition comprising a photoconductor and a binder for saidphotoconductor comprising a polyester having 2-80% repeating and 20-98%of wherein Z is an alkylene group having 2 to 10 carbon atoms, and D andE are each selected from the group consisting of a hydrogen atom, ahalogen atom, an aryl group, an alkyl group, an aryloxy group and analkoxy wherein Z is an alkylene group having 2 to 10 carbon atoms, and Dand E are each selected from the group consisting of a hydrogen atom, ahalogen atom, an aryl group, an alkyl group, an aryloxy group and analkoxy group.

5. The electrophotographic element of claim 4 wherein Z is selected fromthe group consisting of t is an integer from 1 to 7;

n and 0 are each integers from 2 to 7;

s is an integer from zero to 7;

u and v are each integers from 0 to 5;

p, q and r are each integers from 2 to 6;

D is selected from the group consisting of an oxygen atom and a sulfuratom;

Q represents the atoms necessary to complete a carbon atom cycloalkylradical;

R and R are each selected from the group consisting of hydrogen and analkyl radical having 1 to 5 carbon atoms; and

R and R are each alkylene radicals.

6. The electrophotographic element of claim 4 wherein the sensitizer isselected from the group consisting of carbocyanine, pyrylium,thiapyrylium and selenapyrylium dye salts.

7. The electrophotographic element of claim 4 wherein the organicphotoconductor is 4,4-benzylidenebis(N,N-

diethyl-m-toluidine) ethyl-co-ethylene isophthalate) as a binder forsaid photoconductive composition.

16. In an electrophotographic process wherein an electrostatic chargepattern is formed on an electrophotographic element by applying auniform charge to the surface of the photoconductive layer and exposingto a light image, the improvement characterized in that saidelectrographic element has a photoconductive layer containing a binderhaving 2-80% repeating units of and 20-98% of l CH: (I?

(N,N-diethyl-rn-toluidine) as an organic photoconductor, 0.005 to about5.0 weight percent of a sensitizer for said photoconductor andpoly(4,4-isopropylidenebisphenoxyethyl-co-trimethylene isophthalate) asa binder for said photoconductive composition.

13. An electrophotographic element capable of reproducing continuoustones comprising a support having coated thereon a photoconductivecomposition comprising 10 to about 60 weight percent of4,4'-benzylidinebis(N,N- diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor andpoly(4,4-isopropylidenebisphenoxyethylco-tetramethylene isophthalate) asa binder for said photoconductive composition.

14. An electrophotographic element capable of reproducing continuoustones comprising a support having coated thereon a photoconductivecomposition comprising 10 to about 60 weight percent of4,4'-benzylidinebis (N,N-diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor andpoly(4,4-isopropylidenebisphenoxyethyl-co-neopentyl isophthalate) as abinder for said photoconductive composition.

15. An electrophotographic element capable of reproducing continuoustones comprising a support having coated thereon a photoconductivecomposition comprising 10 to about 60 weight percent of4,4'-benzylidinebis (N,N-diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor and poly(4,4-isopropylidenebisphenoxywherein Z is analkylene group having 2 to 10 carbon atoms, and D and E are eachselected from the group consisting of a hydrogen atom, a halogen atom,an aryl group, an alkyl group, an aryloxy group and an alkoxy group.

The British Journal of Photography (September 1964), pp. 784-787.

Conix, Thermoplastic Polyesters from Bisphenols, Industrial andEngineering Chemistry, vol 51, No. 2 (February 1959), pp. 147-150.

CHARLES E. VAN HORN, Primary Examiner US. Cl. X.R.

( 58 @E'HMEAEE W @QRKEQTWN P t 3,7 3,37 me a November 21, 1972Inventor(s) stwalt H. Merrill It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, line 7, "l6 should read --3l---; m? line 23, "16" should read---3l--..

Signed and sealed tfiis 12th day Of June 19 73.

(SEAL) Attes't:

EDW M.PLETQHER,JR. ROBERT GOTTSCHALK Attest ng Offlcer I Commissioner ofPatents:

